H. Ahmed et al., “Multichannel Superposition of Grafted Perfect Vortex Beams,”10.1002/adma.202203044__Advanced Materials, vol. 34, no. 30, Art. no. 2203044, 2022, doi:10.1002/adma.202203044 .

P. Held, M. Engelkemeier, S. De, S. Barkhofen, J. Sperling, and C. Silberhorn, “Driven Gaussian quantum walks,”10.1103/physreva.105.042210__Physical Review A, vol. 105, no. 4, Art. no. 042210, 2022, doi:10.1103/physreva.105.042210 .

B. Liu, L. Huang, and T. Zentgraf, “Efficient Third-harmonic Generation Control with Ultrathin Dielectric Geometric-phase Metasurface,”10.1364/cleo_qels.2022.fth1a.7__presented at the CLEO: QELS_Fundamental Science 2022, San Jose, USA, 2022, doi:10.1364/cleo_qels.2022.fth1a.7 .

F. Spreyer, C. Ruppert, P. Georgi, and T. Zentgraf, “Influence of Plasmon Resonances and Symmetry Effects on Second Harmonic Generation in W–Plasmonic Hybrid Metasurfaces,”10.1021/acsnano.1c06693__ACS Nano, vol. 15, no. 10, pp. 16719–16728, 2021, doi:10.1021/acsnano.1c06693 .

M. Santandrea, M. Stefszky, and C. Silberhorn, “General analytic theory of classical collinear three-wave mixing in a monolithic cavity,”10.1088/2040-8986/ac0b90__Journal of Optics, Art. no. 085803, 2021, doi:10.1088/2040-8986/ac0b90 .

M. Kismann, D. T. Riedl, and P. D. J. K. Lindner, “Ordered arrays of Si nanopillars with alternating diameters fabricated by nanosphere lithography and metal-assisted chemical etching,” Materials Science in Semiconductor Processing, 2021.

D. Emmrich, A. Wolff, N. Meyerbröker, J. Lindner, A. Beyer, and A. Gölzhäuser, “Scanning transmission helium ion microscopy on carbon nanomembranes,” Beilstein Journal of Nanotechnology, pp. 222–231, 2021.

D. Frese, Q. Wei, Y. Wang, M. Cinchetti, L. Huang, and T. Zentgraf, “Nonlinear Bicolor Holography Using Plasmonic Metasurfaces,” ACS Photonics, vol. 8, no. 4, pp. 1013–1019, 2021.

P. Georgi et al., “Optical secret sharing with cascaded metasurface holography,” Science Advances, vol. 7, no. 16, 2021.

S. S. Kruk, W. Gao, D.-Y. Choi, T. Zentgraf, S. Zhang, and Y. Kivshar, “Nonlinear Imaging of Nanoscale Topological Corner States,” Nano Letters, vol. 21, no. 11, pp. 4592–4597, 2021.

J. Mundry, F. Spreyer, V. Jmerik, S. Ivanov, T. Zentgraf, and M. Betz, “Nonlinear metasurface combining telecom-range intersubband transitions in GaN/AlN quantum wells with resonant plasmonic antenna arrays,” Optical Materials Express, vol. 11, no. 7, 2021.

G. Yoon, T. Tanaka, T. Zentgraf, and J. Rho, “Recent progress on metasurfaces: applications and fabrication,” Journal of Physics D: Applied Physics, vol. 54, 2021.

T. Leuteritz et al., “Dielectric travelling wave antennas for directional light emission,” Optics Express, vol. 29, no. 10, 2021.

J. Lu et al., “Observing 0D subwavelength-localized modes at ~100 THz protected by weak topology,”10.1126/sciadv.abl3903__Science Advances, vol. 7, no. 49, Art. no. eabl3903, 2021, doi:10.1126/sciadv.abl3903 .

D. Frese, B. Sain, H. Zhou, Y. Wang, L. Huang, and T. Zentgraf, “A wavelength and polarization selective photon sieve for holographic applications,”10.1515/nanoph-2021-0440__Nanophotonics, vol. 10, no. 18, pp. 4543–4550, 2021, doi:10.1515/nanoph-2021-0440 .

S. De et al., “Effects of coherence on temporal resolution,”10.1103/physrevresearch.3.033082__Physical Review Research, vol. 3, no. 3, Art. no. 033082, 2021, doi:10.1103/physrevresearch.3.033082 .

V. Ansari et al., “Achieving the Ultimate Quantum Timing Resolution,”10.1103/prxquantum.2.010301__PRX Quantum, vol. 2, Art. no. 010301, 2021, doi:10.1103/prxquantum.2.010301 .

V. Roman-Rodriguez et al., “Continuous variable multimode quantum states via symmetric group velocity matching,”10.1088/1367-2630/abef96__New Journal of Physics, vol. 23, Art. no. 043012, 2021, doi:10.1088/1367-2630/abef96 .

L. Padberg, C. Eigner, M. Santandrea, and C. Silberhorn, “Production of waveguides made of materials from the KTP family.” 2021.

A. Ferreri et al., “Multimode integrated SU(1,1) interferometer,”10.1364/cleo_qels.2021.ftu1n.6__2021, doi:10.1364/cleo_qels.2021.ftu1n.6 .

E. Pelucchi et al., “The potential and global outlook of integrated photonics for quantum technologies,”10.1038/s42254-021-00398-z__Nature Reviews Physics, vol. 4, no. 3, pp. 194–208, 2021, doi:10.1038/s42254-021-00398-z .

J. Gil López et al., “Improved non-linear devices for quantum applications,”10.1088/1367-2630/ac09fd__New Journal of Physics, Art. no. 063082, 2021, doi:10.1088/1367-2630/ac09fd .

J. Gil López et al., “Universal compressive tomography in the time-frequency domain,”10.1364/optica.427645__Optica, Art. no. 1296, 2021, doi:10.1364/optica.427645 .

K. H. Luo et al., “Quantum optical coherence: From linear to nonlinear interferometers,”10.1103/physreva.104.043707__Physical Review A, 2021, doi:10.1103/physreva.104.043707 .

D. Bagrets et al., “Probing the topological Anderson transition with quantum walks,”10.1103/physrevresearch.3.023183__Physical Review Research, 2021, doi:10.1103/physrevresearch.3.023183 .

A. Geraldi et al., “Transient subdiffusion via disordered quantum walks,”10.1103/physrevresearch.3.023052__Physical Review Research, 2021, doi:10.1103/physrevresearch.3.023052 .

J. Tiedau, M. Engelkemeier, B. Brecht, J. Sperling, and C. Silberhorn, “Statistical Benchmarking of Scalable Photonic Quantum Systems,”10.1103/physrevlett.126.023601__Physical Review Letters, vol. 126, Art. no. 023601, 2021, doi:10.1103/physrevlett.126.023601 .

N. Prasannan, S. De, S. Barkhofen, B. Brecht, C. Silberhorn, and J. Sperling, “Experimental entanglement characterization of two-rebit states,”10.1103/physreva.103.l040402__Physical Review A, vol. 103, 2021, doi:10.1103/physreva.103.l040402 .

M. Riabinin, P. Sharapova, T. Bartley, and T. Meier, “Generating two-mode squeezing with multimode measurement-induced nonlinearity,”10.1088/2399-6528/abeec2__Journal of Physics Communications, vol. 5, no. 4, 2021, doi:10.1088/2399-6528/abeec2 .

J. Brockmeier et al., “Non-Invasive Visualization of Ferroelectric Domain Structures on the Non-Polar y-Surface of KTiOPO4 via Raman Imaging,”10.3390/cryst11091086__Crystals, Art. no. 1086, 2021, doi:10.3390/cryst11091086 .

M. Hajlaoui et al., “Extremely low-energy ARPES of quantum well states in cubic-GaN/AlN and GaAs/AlGaAs heterostructures,”10.1038/s41598-021-98569-6__Scientific Reports, vol. 11, Art. no. 19081, 2021, doi:10.1038/s41598-021-98569-6 .

M. Santandrea, M. Stefszky, G. Roeland, and C. Silberhorn, “Interferometric method for determining the losses of spatially multi-mode nonlinear waveguides based on second harmonic generation,”10.1364/oe.380788__Optics Express, Art. no. 5507, 2020, doi:10.1364/oe.380788 .

T. Chantakit et al., “All-dielectric silicon metalens for two-dimensional particle manipulation in optical tweezers,” Photonics Research, vol. 8, no. 9, pp. 1435–1440, 2020.

L. Zhu et al., “A dielectric metasurface optical chip for the generation of cold atoms,” Science Advances, vol. 6, no. 31, 2020.

M. Rosenthal, J. K. N. Lindner, U. Gerstmann, A. Meier, W. G. Schmidt, and R. Wilhelm, “A photoredox catalysed Heck reaction via hole transfer from a Ru(II)-bis(terpyridine) complex to graphene oxide ,” Royal Society of Chemistry , vol. 10, no. 42930–42937, 2020.

T. Zentgraf, S. Chen, G. Li, and S. Zhang, “Plasmonic metasurfaces for controlling harmonic generations,” in Nanoantennas and Plasmonics: Modelling, design and fabrication, D. H. Werner, S. D. Campbell, and L. Kang, Eds. The Institution of Engineering and Technology, 2020.

R. Tischendorf et al., “Examination of the evolution of iron oxide nanoparticles in flame spray pyrolysis by tailored in situ particle sampling techniques,” Journal of Aerosol Science, 2020.

J. Bürger, T. Riedl, and J. K. N. Lindner, “Influence of lens aberrations, specimen thickness and tilt on differential phase contrast STEM images,” Ultramicroscopy, 2020.

M. Stefszky et al., “Waveguide resonator with an integrated phase modulator for second harmonic generation,”10.1364/oe.412824__Optics Express, Art. no. 1991, 2020, doi:10.1364/oe.412824 .

B. Sain and T. Zentgraf, “Metasurfaces help lasers to mode-lock,” Light: Science &; Applications, vol. 9, p. 67, 2020.

H. Zhou et al., “Polarization-Encrypted Orbital Angular Momentum Multiplexed Metasurface Holography,” ACS Nano, vol. 14, no. 5, pp. 5553–5559, 2020.

C. Schlickriede, S. S. Kruk, L. Wang, B. Sain, Y. Kivshar, and T. Zentgraf, “Nonlinear imaging with all-dielectric metasurfaces,” Nano Letters, vol. 20, no. 6, pp. 4370–4376, 2020.

F. Spreyer, R. Zhao, L. Huang, and T. Zentgraf, “Second harmonic imaging of plasmonic Pancharatnam-Berry phase metasurfaces coupled to monolayers of W,” Nanophotonics, vol. 9, no. 2, pp. 351–360, 2020.

B. Liu et al., “Nonlinear Wavefront Control by Geometric-Phase Dielectric Metasurfaces: Influence of Mode Field and Rotational Symmetry,” Advanced Optical Materials, vol. 8, no. 9, 2020.

B. Atorf, H. Mühlenbernd, T. Zentgraf, and H.-S. Kitzerow, “All-optical switching of a dye-doped liquid crystal plasmonic metasurface,”10.1364/oe.383877__Optics Express, vol. 28, no. 6, pp. 8898–8908, 2020, doi:10.1364/oe.383877 .

J. Tiedau, T. Schapeler, V. Anant, H. Fedder, C. Silberhorn, and T. Bartley, “Single-channel electronic readout of a multipixel superconducting nanowire single photon detector,”10.1364/oe.383111__Optics Express, vol. 28, no. 4, Art. no. 5528, 2020, doi:10.1364/oe.383111 .

M. Santandrea, M. Stefszky, G. Roeland, and C. Silberhorn, “Interferometric method for determining the losses of spatially multi-mode nonlinear waveguides based on second harmonic generation.,”10.1364/oe.380788__Optics Express, vol. 28, no. 4, Art. no. 5507, 2020, doi:10.1364/oe.380788 .

S. Mukamel et al., “Roadmap on quantum light spectroscopy,”10.1088/1361-6455/ab69a8__Journal of Physics B: Atomic, Molecular and Optical Physics, vol. 53, no. 7, Art. no. 072002, 2020, doi:10.1088/1361-6455/ab69a8 .

E. Meyer-Scott, C. Silberhorn, and A. Migdall, “Single-photon sources: Approaching the ideal through         10.1063/5.0003320__multiplexing,”10.1063/5.0003320__Review of Scientific Instruments, vol. 91, no. 4, Art. no. 041101, 2020, doi:10.1063/5.0003320 .

T. Dirmeier et al., “Distillation of squeezing using an engineered pulsed parametric down-conversion source,”10.1364/oe.402178__Optics Express, vol. 28, no. 21, Art. no. 30784, 2020, doi:10.1364/oe.402178 .

C. Eigner, L. Padberg, M. Santandrea, H. Herrmann, B. Brecht, and C. Silberhorn, “Spatially single mode photon pair source at 800 nm in periodically poled Rubidium exchanged KTP waveguides,”10.1364/oe.399483__Optics Express, vol. 28, no. 22, Art. no. 32925–32935, 2020, doi:10.1364/oe.399483 .

A. Ferreri, V. Ansari, B. Brecht, C. Silberhorn, and P. R. Sharapova, “Spatial entanglement and state engineering via four-photon Hong–Ou–Mandel interference,”10.1088/2058-9565/abb411__Quantum Science and Technology, vol. 5, no. 4, Art. no. 045020, 2020, doi:10.1088/2058-9565/abb411 .

J. Sperling et al., “Detector-Agnostic Phase-Space Distributions,”10.1103/physrevlett.124.013605__Physical Review Letters, 2020, doi:10.1103/physrevlett.124.013605 .

M. Engelkemeier et al., “Quantum photonics with active feedback loops,”10.1103/physreva.102.023712__Physical Review A, vol. 102, Art. no. 023712, 2020, doi:10.1103/physreva.102.023712 .

T. Nitsche et al., “Local Versus Global Two-Photon Interference in Quantum Networks,”10.1103/physrevlett.125.213604__Physical Review Letters, 2020, doi:10.1103/physrevlett.125.213604 .

F. Schmidt et al., “Free and defect-bound (bi)polarons in LiNbO3: Atomic structure and spectroscopic signatures from ab initio calculations,”10.1103/PhysRevResearch.2.043002__Physical Review Research, vol. 2, no. 4, Art. no. 043002, 2020, doi:10.1103/PhysRevResearch.2.043002 .

M. Rosenthal, J. Lindner, U. Gerstmann, A. Meier, W. G. Schmidt, and R. Wilhelm, “A photoredox catalysed Heck reaction via hole transfer from a Ru(ii)-bis(terpyridine) complex to graphene oxide,”10.1039/d0ra08749a__RSC Advances, vol. 10, no. 70, pp. 42930–42937, 2020, doi:10.1039/d0ra08749a .

A. Bocchini, C. Eigner, C. Silberhorn, W. G. Schmidt, and U. Gerstmann, “Understanding gray track formation in KTP: Ti^3+ centers studied from first principles,”10.1103/PhysRevMaterials.4.124402__Phys. Rev. Materials, vol. 4, p. 124402, 2020, doi:10.1103/PhysRevMaterials.4.124402 .

K. Engelkemeier et al., “Nano-architectural complexity of zinc oxide nanowall hollow microspheres and their structural properties,”10.1088/1361-6528/ab55bc__Nanotechnology, vol. 31, p. 095701, 2020, doi:10.1088/1361-6528/ab55bc .

L. Padberg et al., “Characterisation of width-dependent diffusion dynamics in rubidium-exchanged KTP waveguides,”10.1364/oe.397074__Optics Express, Art. no. 24353, 2020, doi:10.1364/oe.397074 .

M. Massaro, E. Meyer-Scott, N. Montaut, H. Herrmann, and C. Silberhorn, “Improving SPDC single-photon sources via extended heralding and feed-forward control,”10.1088/1367-2630/ab1ec3__New Journal of Physics, Art. no. 053038, 2019, doi:10.1088/1367-2630/ab1ec3 .

M. Santandrea, M. Stefszky, G. Roeland, and C. Silberhorn, “Characterisation of fabrication inhomogeneities in Ti:LiNbO3 waveguides,”10.1088/1367-2630/ab5cb5__New Journal of Physics, Art. no. 123005, 2019, doi:10.1088/1367-2630/ab5cb5 .

M. Santandrea, M. Stefszky, V. Ansari, and C. Silberhorn, “Fabrication limits of waveguides in nonlinear crystals and their impact on quantum optics applications,”10.1088/1367-2630/aaff13__New Journal of Physics, Art. no. 033038, 2019, doi:10.1088/1367-2630/aaff13 .

K.-H. Luo et al., “Counter-propagating photon pair generation in a nonlinear waveguide,”10.1364/oe.378789__Optics Express, Art. no. 3215, 2019, doi:10.1364/oe.378789 .

K. Engelkemeier et al., “Nano-architectural complexity of zinc oxide nanowall hollow microspheres and their structural properties,” Nanotechnology, 2019.

B. Sain, C. Meier, and T. Zentgraf, “Nonlinear optics in all-dielectric nanoantennas and metasurfaces: a review,” Advanced Photonics, vol. 1, no. 2, p. 024002, 2019.

E. Meyer-Scott et al., “Engineering integrated photon pair sources and multiplexed detectors (Conference Presentation),”10.1117/12.2513753__in Advances in Photonics of Quantum Computing, Memory, and Communication XII, 2019, doi:10.1117/12.2513753 .

C. Golla, N. Weber, and C. Meier, “Zinc oxide based dielectric nanoantennas for efficient nonlinear frequency conversion,” Journal of Applied Physics, vol. 125, no. 7, 2019.

M. Protte, N. Weber, C. Golla, T. Zentgraf, and C. Meier, “Strong nonlinear optical response from ZnO by coupled and lattice-matched nanoantennas,” Journal of Applied Physics, vol. 125, 2019.

D. Frese, Q. Wei, Y. Wang, L. Huang, and T. Zentgraf, “Nonreciprocal Asymmetric Polarization Encryption by Layered Plasmonic Metasurfaces,”10.1021/acs.nanolett.9b01298__Nano Letters, vol. 19, no. 6, pp. 3976–3980, 2019, doi:10.1021/acs.nanolett.9b01298 .

T. Li et al., “Reconfigurable metasurface hologram by utilizing addressable dynamic pixels,” Optics Express, vol. 27, no. 15, pp. 21153–21162, 2019.

B. Reineke et al., “Silicon metasurfaces for third harmonic geometric phase manipulation and multiplexed holography,” Nano Letters, vol. 19, no. 9, pp. 6585–6591, 2019.

P. Georgi et al., “Metasurface interferometry toward quantum sensors,”10.1038/s41377-019-0182-6__Light: Science &; Applications, vol. 8, p. 70, 2019, doi:10.1038/s41377-019-0182-6 .

R. Köthemann, N. Weber, J. K. N. Lindner, and C. Meier, “High-precision determination of silicon nanocrystals: optical spectroscopy versus electron microscopy,” Semiconductor Science and Technology, vol. 34, no. 9, 2019.

Q. Wei et al., “Simultaneous Spectral and Spatial Modulation for Color Printing and Holography Using All-dielectric Metasurfaces,” Nano Letters, vol. 19, no. 12, pp. 8964–8971, 2019.

Z. Lin, L. Huang, Z. T. Xu, X. Li, T. Zentgraf, and Y. Wang, “FourWave Mixing Holographic Multiplexing Based on Nonlinear Metasurfaces,” Advanced Optical Materials, vol. 7, no. 21, p. 1900782, 2019.

Z. Lin et al., “Dynamic control of mode modulation and spatial multiplexing using hybrid metasurfaces,” Optics Express, vol. 27, no. 13, pp. 18740–18750, 2019.

S. Suwannasopon et al., “Miniaturized Metalens Based Optical Tweezers on Liquid Crystal Droplets for Lab-on-a-Chip Optical Motors,” Crystals, vol. 9, no. 10, p. 515, 2019.

S. Chen, B. Reineke, G. Li, T. Zentgraf, and S. Zhang, “Strong Nonlinear Optical Activity Induced by Lattice Surface Modes on Plasmonic Metasurface,” Nano Letters, vol. 19, no. 9, pp. 6278–6283, 2019.

L. Padberg, C. Eigner, M. Santandrea, and C. Silberhorn, “Herstellung von Wellenleitern aus Materialien der KTP-Familie.” 2019.

Z. Xie et al., “Efficient C-band single-photon upconversion with chip-scale Ti-indiffused pp-LiNbO<sub>3</sub> waveguides,”10.1364/ao.58.005910__Applied Optics, vol. 58, no. 22, Art. no. 5910, 2019, doi:10.1364/ao.58.005910 .

I. I. Faruque et al., “Estimating the Indistinguishability of Heralded Single Photons Using Second-Order Correlation,”10.1103/physrevapplied.12.054029__Physical Review Applied, vol. 12, no. 5, Art. no. 054029, 2019, doi:10.1103/physrevapplied.12.054029 .

A. Ferreri, V. Ansari, C. Silberhorn, and P. R. Sharapova, “Temporally multimode four-photon Hong-Ou-Mandel interference,”10.1103/physreva.100.053829__Physical Review A, vol. 100, no. 5, Art. no. 053829, 2019, doi:10.1103/physreva.100.053829 .

J. Vondran et al., “Spatially asymmetric transients of propagating exciton-polariton modes in a planar CdZnTe/CdMgTe guiding structure,”10.1103/physrevb.100.155308__Physical Review B, vol. 100, no. 15, p. 155308, 2019, doi:10.1103/physrevb.100.155308 .

J. Sperling, A. Perez-Leija, K. Busch, and C. Silberhorn, “Mode-independent quantum entanglement for light,”10.1103/physreva.100.062129__Physical Review A, 2019, doi:10.1103/physreva.100.062129 .

J. Sperling, E. Meyer-Scott, S. Barkhofen, B. Brecht, and C. Silberhorn, “Experimental Reconstruction of Entanglement Quasiprobabilities,”10.1103/physrevlett.122.053602__Physical Review Letters, 2019, doi:10.1103/physrevlett.122.053602 .

M. Riabinin, P. Sharapova, T. Bartley, and T. Meier, “Generating two-mode squeezing with multimode measurement-induced nonlinearity,” arXiv:1912.09097. 2019.

K. Brassat et al., “On the Adsorption of DNA Origami Nanostructures in Nanohole Arrays,” Langmuir, 2018.

K. Brassat et al., “On the Adsorption of DNA Origami Nanostructures in Nanohole Arrays,” Langmuir, vol. 34, pp. 14757–14765, 2018.

M. Kismann, T. Riedl, X. Wu, T. Wagner, and J. Lindner, “Photonic crystal properties of Si and SiO2 nanopillar arrays fabricated by nanosphere lithography and metal-assisted wet-chemical etching,” presented at the EMRS-Fall Meeting 2018, Warsaw (Poland), 2018.

T. Riedl, V. Kunnathully, A. Trapp, D. Reuter, and J. Lindner, “Strain Relaxation in InAs Nanoislands on top of GaAs (111) A Nanopillars,” presented at the 14th International Conference on Atomically Controlles Surfaces, Interfaces and Nanostructures (ACSIN-14), Sendai (Japan), 2018.

T. Riedl, V. Kunnathully, A. Trapp, D. Reuter, and J. Lindner, “MBE Growth of InAs on Nanopillar-Patterned GaAs (111) A ,” presented at the 14th International Conference on Atomically Controlles Surfaces, Interfaces and Nanostructures (ACSIN-14), Sendai (Japan), 2018.

A. W. Achtstein et al., “Impact of shell growth on recombination dynamics and exciton-phonon interaction in CdSe-CdS core-shell nanoplatelets,” accepted 05.09.2018.

K. Brassat, T. Riedl, and J. Lindner, “Self-assembled Surface Patterns for Controlled Nanoparticle Placement and Improved Semiconductor Heteroepitaxy,” presented at the 12th International 12th International Conference on Physics of Advanced Materials (ICPAM-12), Heraklion (Greece), 2018.

R. Scott et al., “Exciton-Phonon Interaction in Core-Only, Core-Shell Nanoplatelets and Quantum Dots ,” submitted to Nano Letters.

T. Riedl and J. Lindner, “Stability of Heteroepitaxial Coherent Growth Modes on Nanowire Radial Surfaces,” submitted to Phys. Rev. Mat.

K. Brassat, D. Kool, and J. Lindner, “Modification of block copolymer lithography masks by O2 plasma treatment: Insights from lift off experiments, nanopore etching and free membranes,” To be submitted.

T. Riedl et al., “Nanostructure Research using Transmission Electron Microscopy at the new OWL Analytic Centre,” presented at the 8th NRW Nano Conference, Dortmund (Germany), 2018.

J. Lindner, “State-of-the-art transmission electron microscopy in the imaging and scanning mode,” presented at the 3rd Autumn School on Physics of Advanced Materials, PAMS-3 / Technological Educational Institute of Crete, Heraklion, Crete (Greece), 2018.

E. Meyer-Scott et al., “Engineering integrated sources of entangled photon pairs,”10.1364/ls.2018.lm3b.1__2018, doi:10.1364/ls.2018.lm3b.1 .